The instant invention relates to a multimode wireless radio access network (RAN) having a distributed signal processing architecture, which can either be part of a wireless service provider's network or comprise an independent enterprise wireless network infrastructure.
Current and envisioned wireless cellular systems employ various air interfaces between the mobile user communication equipment (UE) and the fixed infrastructure of the Public Land Mobile Network (PLMN). Examples of widely deployed air interfaces, commonly labeled as second generation (2G) networks, include IS-95 (CDMA), IS-136 (TDMA), and GSM. Examples of third generation (3G) wireless networks, more advanced than the 2G networks and in the process of standardization or deployment, include UMTS (WCDMA) and CDMA2000.
The 2G and 3G network architectures consist of two major sub-networks: (a) the radio access network (RAN), and (b) the Core Network (CN). The RAN controls the radio physical aspects of the UE, and the CN controls the UE's access to applications supported by the wireless service provider or external public or private networks, such as the Internet. The wireless service providers typically own and operate both the RAN and CN sub-networks. The traditional wireless network architecture includes the UE, RAN, CN, and the wireless interfaces to network applications.
The traditional RAN has two major components, the radio base station (BS) and the base station controller (BSC). The single-mode RAN of the prior art comprises a multitude of BS/BSC associations depending on the system capacity and coverage area Each BSC controls a cluster of BS's dedicated to the same specific single radio access mode.
The UE employs two levels of signaling protocols for establishing the service connection with a wireless communication network: (1) a signaling protocol stack between the UE and the CN for connection set-up specifications; and (2) a signaling protocol stack between the UE and the RAN for establishing a radio channel with characteristics consistent with the desired UE-CN service connection.
The initial communications for exchanging signaling protocol messages between the UE and the CN and the UE and the RAN use pre-established common radio resources between the UE and the wireless network. The signaling protocol(s) between the UE and CN are well-established. That between the UE and the RAN, referred to as the Radio Resource Control protocol, has the protocol entity resident at the BSC. In the existing art, both control and data information streams are processed by the BSC.
The BSC controls the radio resources of the BS to establish the radio physical connections, i.e., the radio transceiver characteristics, between the UE and the BS and the ground communications link between the BS and its associated BSC. The BSC employs a signaling protocol with the CN to establish the ground communication link between the BSC and its corresponding entity in the CN. Once all the links are established, the data streams are exchanged between the UE and BS, the BS and the BSC, and the BSC and the CN. The communications between the BS and the BSC and between the BSC and the CN consist of both control and application data information.
The traditional BSC comprises a monolithic and rigid RAN component. It uses fixed dedicated connections with its associated BSs for processing the control signals and the single mode radio access data streams. This limits the wireless service provider's ability to (a) increase the RAN capacity because of the single mode operation limitation, and (b) minimize the impact of BSC outage on wireless service availability, because a fault at the BSC shuts down further communication.
The layered protocol model specific to the traditional single radio access mode is a three-layer structure: the Physical layer (layer 1), the Media Access Control and Radio Link Control layer (layer 2), and the Radio Resource Control (RRC) layer (layer 3). Each of these layers employs technology dedicated to the same specific single radio access mode.
Various methods to implement multiple radio access mode communication, such as using IEEE 802.11 and 3G UMTS and their variants, have been proposed or implemented. [e.g. IEEE Standards 802.11b, a, g, n (http://standards.ieee.org); 3rd Generation Partnership Project, 3GPP, Technical Specifications and Technical Reports for a 3rd Generation Mobile System (www.3gpp.org); 3GPP TR 22.934, “Feasibility Study on 3GPP System to Wireless Local Area Network (WLAN) Interworking”]. The focus has been on inter-working the radio link modes constituting separate Radio Access Networks (RANs), using one of two schemes that vary in the degree of control and interactions between the networks: Loose Coupling and Tight Coupling. The choice of the coupling scheme has a direct effect on the service performance in the case where the mobile users are handed off from one radio access mode to the other [R. Samarasinghe, V. Friderikos, A. H. Aghavami “Analysis of Intersystem Handover: UMTS FDD & WLAN”, London Communications Symposium, 8-9 Sep., 2003].
An example of a RAN architecture that aims to mitigate issues related to integrated BSC functionality in the UMTS Terrestrial RAN (UTRAN) has been described by Siemens. [3GPP TSG-RAN WG3 Meeting #36, “Proposed Architecture for UTRAN Evolution,” Marne-la-Vallee, 19-23 May 2003.] While decomposing the functionality of a Radio Network Controller (RNC) into two entities—a signaling entity and a data processing entity (DPE), the scheme fails to provide the instant invention's distributed architecture for multimode functionality. (The RNC is the equivalent of the BSC in the 3GPP UMTS standards.) Although the DPEs are inter-linked, each BS has a fixed connection with a specific DPE, which processes both the signaling traffic and the data traffic between them. Consequently, this scheme too suffers from the low network outage tolerance limitation of the other prior art. A fault at the DPE renders the network inaccessible, and further communication impossible.
The prior art schemes employing fixed connections between the BS and the BSC also suffer from less than optimal handoff of mobile UE equipment from one BSC to another. If the new BS lacks a connection with the currently used BSC, the UE connection must be switched to a BSC connected to the new BS. This requires the connection between the BSC and the core network (CN) to be altered, resulting in a less efficient handoff. Because the DPEs are inter-linked in the Siemens approach, however, changing the connection to the CN may be avoided by transferring the data traffic directly from the old to the new DPE. Although more desirable than the alternative, this process incurs traffic delays while also requiring increased infrastructure bandwidth.
Current wireless network deployments handle two types of traffic, the circuit-switched (CS) traffic and the packet-switched (PS) traffic. The former refers to the mobile voice telephony service that ties into the legacy telephony network. The latter corresponds to the mobile access to data networks, such as the Internet. The CS and PS traffic flows are handled separately in the Core Network (CN) by different equipment, comprising the CS and PS domains. A current thrust in wireless technology is to support CS services within the PS domain, eliminating the need for the CS domain. This way, the PS data traffic will support multi-media services, including voice and video. As an intermediate step, the CS domain has witnessed major changes, including use of packet-based connection links between the RAN and the CS domain equipment. This has resulted in separate traffic flows for system signaling and user traffic, consistent with the PS domain's requirements. Where the CS Domain is implemented using such a paradigm, the instant invention is readily applicable to both the PS and CS domains, including multimedia data streams comprising voice and video.